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   <title>Zoltan User's Guide:  Ordering Algorithms</title>
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<div align=right><b><i><a href="ug.html">Zoltan User's Guide</a>&nbsp;
|&nbsp; <a href="ug_order_parmetis.html">Next</a>&nbsp; |&nbsp; <a href="ug_alg_hier.html">Previous</a></i></b></div>
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<h2>
<a NAME="Ordering Algorithms"></a>Ordering Algorithms</h2>
The following graph (sparse matrix) ordering algorithms are currently included in the Zoltan toolkit:
<blockquote>
<a href="ug_order_parmetis.html">Nested dissection by METIS/ParMETIS </a><br>
<a href="ug_order_ptscotch.html">Nested dissection by Scotch/PT-Scotch</a><br>
<a href="ug_order_local_hsfc.html">Local ordering with Hilbert space filling curves</a>
</blockquote>
These methods produce orderings for various applications (e.g., reducing fill in sparse matrix factorizations).
Ordering is accessed through calls to 
<b><a href="ug_interface_order.html#Zoltan_Order">Zoltan_Order</a></b>.
<p><!---------------------------------------------------------------------------->

<h3>
<b>Third-party libraries</b>
</h3>
Currently, most ordering in Zoltan is provided through the third-party libraries METIS/ParMETIS and PT-Scotch. 
The one exception is the local Hilbert space filling curve ordering.
To use the other methods, a third-party library must be present.

<h3>
<a NAME="Order Parameters"></a>
<hr><b>Ordering Parameters</b></h3>
While the overall behavior of Zoltan is controlled by <a href="ug_param.html">general
Zoltan parameters</a>, the behavior of each ordering method is controlled
by parameters specific to ordering which are also set by calls to <b><a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a></b>.
Many of these parameters are specific to individual ordering algorithms,
and are listed in the descriptions of the individual algorithms.&nbsp;
However, several have meaning across multiple ordering algorithms. These
parameters are described below.
<br>&nbsp;
<table WIDTH="100%" NOSAVE >
<tr VALIGN=TOP>
<td VALIGN=TOP><b>Parameters:</b></td>

<td></td>
</tr>

<tr VALIGN=TOP NOSAVE>
<td NOSAVE><a NAME="ORDER_METHOD"></a>&nbsp;&nbsp; <i>ORDER_METHOD</i></td>

<td>The order algorithm used by Zoltan is specified by this parameter.
Valid values are&nbsp;
<blockquote>
"METIS" (sequential <a href="ug_order_parmetis.html">nodal nested dissection by METIS</a>),
<br>"PARMETIS" (parallel <a href="ug_order_parmetis.html">nodal nested dissection by ParMETIS </a>), 
<br>"SCOTCH" (sequential ordering using <a href="ug_order_ptscotch.html">Scotch</a>),
<br>"PTSCOTCH" (parallel ordering using <a href="ug_order_ptscotch.html">PT-Scotch</a>), 
<br>"LOCAL_HSFC" (local ordering using <a href="ug_order_local_hsfc.html">Hilbert space filling curves</a>), and
<br>"NONE" (for no ordering).
</blockquote>
</td>
</tr>



<tr VALIGN=TOP>
<td VALIGN=TOP><a NAME="Default_Parameter_Values"></a><b>Default Values:</b></td>

<td></td>
</tr>

<tr VALIGN=TOP>
<td></td>

<td><i>ORDER_METHOD</i> = PARMETIS (with MPI), METIS (when no MPI)</td>
</tr>





</table>

<p><!---------------------------------------------------------------------------->
<hr WIDTH="100%">[<a href="ug.html">Table of Contents</a>&nbsp; | <a href="ug_order_parmetis.html">Next:&nbsp;
Nested dissection by ParMETIS</a>&nbsp; |&nbsp; <a href="ug_alg_hier.html">Previous:&nbsp;
Hybrid Hierarchical Partitioning</a>&nbsp; |&nbsp; <a href="https://www.sandia.gov/general/privacy-security/index.html">Privacy and Security</a>]
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